Room within a Room, Warehouse with loud overhead

[bdkauff]

Hello all! First time poster, long-time lurker.

I'm a composer planning to build a "room-within-a-room" in a large warehouse space that my theater company rents.

Goals
Since I'm going to be doing a lot of composing, mixing and some small-scale recording, the priority for the room is for it to be quiet enough amidst the activity of the building. I think that's the biggest challenge--the building is a warehouse-style office building, and the "ceilings" of our unit are basically the floorboards of the floor above us. You can hear almost everything going on above.

We are not generating a lot of loud music, most common loudest instrument being piano. If anything we record pretty quiet stuff (cello, acoustic guitar, vocals, voice-over).

Room
The floor is thick concrete above earth, so I don't plan on floating the floor. The room will be a rectangle ~22'x17'x12', situated in the corner of the existing unit, so two of the "outer" walls of the studio will be the brick walls that form the larger unit. The ceiling of the unit has all kinds of pipes, conduit, etc., so the idea is for the studio ceiling to sit on the walls only, but below the pipes above us.

HVAC
The unit has HVAC and the building is very efficient, so for the studio room, we don't plan on needing heat. For AC, we're looking into a standalone floor unit outside the room that can feed air into the room via a short duct.

Drawings
I've attached some pictures which were created for the benefit of myself and the general contractor we're working with, cobbled together from this website mostly. If its not clear from the drawings , I am not a builder, so these are mainly to bring attention to the contractor some of the acoustic-specific techniques to use.

Questions
Besides general advice, I'd love to know:

If there's anything else I can do to mitigate noise from above? Should I add more mass below the floor above us? I've done my best to communicate to the contractor the importance of COMPLETELY decoupling this room from the rest of the building, but if there's anything about the drawings I can improve to make it clearer, I'm all ears.

Is a 6" airgap sufficient?

Should I employ sound isolation clips/hat channel in addition to the ceiling airgap and treatment of floor above?

If a standalone AC unit can be found, should I plan on building a silencing box, or is it not neccessary?

If helpful to know, our budget is ~$15K and our landlord has agreed to kick in another $5K.

Thanks in advance for any help/advice!

Ben

[gullfo]

that is the right overall approach - consider that with a gap of 1" between 2 2x6 walls you're getting 12" of space between the mass layers. so a 6" gap between frames isn't really necessary.
one thing to check - get a hold of a mechanics stethoscope and listen to the noise in the ceiling and the floor. once you create sufficient isolation in the new ceiling and walls, the floor becomes the main source of inbound and outbound sounds. if there is more noise than you expect (esp low frequencies, chair scraping, thuds from walking and people dropping things) you'll want to know that sooner rather than later because you might then float an isolation booth/room (but maybe not the control room) to reduce the risk of noise getting into your recordings from live mics.
depending on the actual ceiling (yours) / floor (theirs) construction - you might do some beefing up and damping of the existing floor, and then consider the transmission loss on an intermediate mass to reduce structural-to-airborne sounds from making its way directly to your inner mass layer.

[bdkauff]

Thanks Gullfo!

...and then consider the transmission loss on an intermediate mass to reduce structural-to-airborne sounds from making its way directly to your inner mass layer.

Can you walk me through this a little more? Not sure I'm following.

[gullfo]

sometimes simply add amass and damping to existing building ceiling/floor - does not completely eliminate sounds making their way through. so one option (at risk of creating a third leaf problem) is to add additional mass on the exterior frame you're creating. for example, in a warehouse with high ceiling (say 4m) and you're planning on your interior ceiling being 3.1m, and your planned exterior framing is only reaching 3.6m, you would add your mass on the outside of the frame, however you now have a potential 3rd leaf (inner mass, exterior mass, building ceiling/floor mass). which depending on the gaps between the building layer and your exterior layer could reduce your isolation at some frequencies.

please note this is true for walls and floated floors as well.

there are several spreadsheet calculators found on the internet regarding transmission loss (M-A-M and studiotips would be a good start).

[bdkauff]

Thanks Glenn, and sorry for the delay.

If I'm understanding you correctly, you're saying I might be able to add additional layers of, say, drywall on top of the interior room essentially? Like above the joists of the interior room?

[gullfo]

yes

[bdkauff]

The more I read and research, the more I'm encountering the pipes as a major issue to any ceiling construction.

From floor to ceiling of the existing warehouse space is ~12'. However the lowest pipe is ~9'. I assume this means my whole interior room needs to be below all the pipes, but I wonder if anyone has any clever ideas about maximizing my isolation and also my interior ceiling height? Should I be exploring outside-in verus inside-out?

Ben

[gullfo]

sometimes you can build channel for the pipes so there are only small sections of the ceiling which need to come down lower than the rest. sometimes you can re-route the pipes. in general it's worst case to lower the entire ceiling to accommodate a pipe or two.

[bdkauff]

Thanks, Glenn. Met with the contractor today at the space. The direction of the joists means we can avoid the pipes pretty easily in constructing the ceiling, so that's a big relief.

I've attached an updating drawing of the ceiling with an "inside-out" approach, since that seems to be ideal according to this site and John's website. In this plan, there's definitely one leaf of mass, but unless we significantly beef up the floor above somehow, I can't tell if we have a true two-leaf system. Is there anything I can change to make the ceiling more robust as far as isolation?

Ben

[gullfo]

so the upstairs floor - if you have nails coming through (common) you can either cut them (hard if they're the square hardwood floor type) or use the rigid "blue" insulation and press it onto the nails then add the requisite 2x 5/8" type X (or equiv) drywall. using cleats on the edges can allow for some flexing of the floor or screw in if the floor is substantially rigid. caulk and more more caulk. to seal it all. if the pipes are prone to noise (drainage sounds, clanging, etc) cover those with a wide rubber tape and/or pipe insulation.

[DanDan]

@ Ben, what drawing program are you using?

[bdkauff]

@ Ben, what drawing program are you using?

Illustrator. These are my totally un-professional attempts at communicating this stuff, so things won't be to scale or correct in many respects, ha! Contractor will have more precise drawings today I think.

[bdkauff]

so the upstairs floor - if you have nails coming through (common) you can either cut them (hard if they're the square hardwood floor type) or use the rigid "blue" insulation and press it onto the nails then add the requisite 2x 5/8" type X (or equiv) drywall. using cleats on the edges can allow for some flexing of the floor or screw in if the floor is substantially rigid. caulk and more more caulk. to seal it all. if the pipes are prone to noise (drainage sounds, clanging, etc) cover those with a wide rubber tape and/or pipe insulation.

Glenn!

[bdkauff]

Do others form a consensus that I need to drywall the ceiling/floor above? Are there ceiling designs other than inside-out I should consider before moving ahead?

[gullfo]

as a note: the addition of the mass to the upper ceiling isn't about an inside out approach - it's about increasing the exterior layer of mass before building the inner room. so you could just add mass onto decoupled hat channel off the joists, of if doing M-A-M then directly attach to joist and then again on inside of the interior framing. just a matter of deicing how you want to handle mass placement.